People are losing their minds after a seemingly little-known maths hack was revealed online.
The discussion was provoked by a Reddit user who asked others on the social media platform if they knew of a “little-known but obvious fact that will immediately make all of us feel stupid?”
In response, one person explained that “percentages are reversible”.
“Eight per cent of 25 is the same as 25 per cent of eight and one of them is much easier to do in your head,” the user wrote.
To elaborate, 25 per cent of eight (or a quarter of eight) is two. Eight per cent of 25 is also two.
Additional examples include:
Fifty per cent of 10 is five. Ten per cent of 50 is also five.
Seventy five per cent of four is three. Four per cent of 75 is also three.
Forty per cent of 60 is 24. Sixty per cent of forty is also 24.
Reddit users were “blown away” by the hack, noting that it will making tipping or splitting bills at restaurants much easier.
“This is life changing,” one person wrote.
Another called it “really useful”.
I am filled with rage at my middle school math teacher right now. pic.twitter.com/14SrDoWfHM
— Every Billionaire Is A Policy Failure (@DanRiffle) January 30, 2020
“I am equally blown away and suddenly feel so content with the enlightenment,” a third said.
However, one person pointed out it might not be useful with bigger numbers.
“While 25 per cent of eight might be easy to do, using this trick when calculating something like 18 per cent of 70 (or 70 per cent of 18) might not be as useful,” they wrote.
“Of course, it's still a neat math trick that might not be intuitive at first but totally makes sense when you think about it.”
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